Certain prior art drive means for flat, thin structures such as sheets, tapes and belts have all been designed so as to drive same without regard to the natural tendencies of the driven structure to wander in a horizontal plane as it passes through an opening between drive and idler rollers.
In devices where the horizontal wandering aforedescribed was a problem, it was the practice of the art to provide guide arms or pins on either and both sides of the driven structure to prevent it from wandering from the drive means. It was also the practice to provide the drive means with a variable axis to change the location of driving torque from the driving axis.
It is to the improvement of the aforesaid drive means by a design which limits (eliminates) horizontal wander that this invention has found utility.
More particularly, the drive means of this invention has as an object a drive which will use contact that varies along a horizontal plane in an oscillating fashion to impart motion to a flat, thin sheet, tape or belt such that any tendency of the latter to wander horizontally is negated.
A more specific statement of the object of this invention is to, in combination with an idler roller, disclose a heretofore unheard of drive roller whose drive surfaces are a returning spiral convolution having the form of a development of an elipse on an otherwise plain roller.
Another object of this invention is to form an idler roller from a plurality of discs that are rotatable relative to and independently of each other for supporting a flat, thin sheet, tape or belt with a helical drive means thereabove so that the drive means is operative upon the flat, thin sheet, tape or belt to cause separate discs to idle therewith.